This invention relates to an apparatus and method for stacking and, more particularly, to relatively flexible products such as paper towels and the like.
In the production of converted paper products (and other products as well), it is frequently desirable to package the product in stacks. For example, C-folded paper towels are frequently sold in packs of 200 towels (stacked). This is a somewhat higher count than that utilized 25 years ago (see co-owned U.S. Pat. 3,254,889) but the problems are the same. It is always a matter of developing square stacks of exact count at high speed.
The towels, for example, are formed continuously by slitting a wide web into five or six narrow strips of web and then longitudinally folding each strip by passing them over folding boards folded strips are t routed to travel combined into a ribbon of stacked strips. The ribbon is cut into towel lengths and these substacks of towels are called clips which are turned 90.degree. before going into the stacker. Apparatus showing this general arrangement can be seen in co-owned British Patent 2,028,774.
Final, salable stacks are formed then by stacking a fixed number of clips to yield the package quantity of towels. The final stacking operation is frequently the speed limiting part of the process and requires complicated mechanical assemblies to run at production speeds. The object of this invention is to simplify the final tacking operation while maintaining or increasing the potential speed of the production line. A further object is to provide ease of stack count changes and flexibility for culling off-specification products.
In the illustrated embodiment of the invention, slotted wheel means is employed in conjunction with endless chain conveyors in the general arrangement seen in our earlier, co-owned U.S. Pat. No. 4,736,936. In the illustrated embodiment of the invention, the endless conveyors are equipped with diving fingers--with the fingers on one conveyor being spaced orbitally from the fingers of the other conveyor so as to develop alternate stacks.
Other pertinent prior art patents are Yamada et al U.S. Pat. No. 4,511,136 which shows a slotted wheel and Merworth U.S. Pat. No. 4,398,455 which shows stacking apparatus employing pairs of conveyors.
The invention is described in conjunction with the illustrative embodiment in the accompanying drawing, in which:
FIG. 1 is a fragmentary side elevational view of apparatus for practicing the invention;
FIG. 2 is a front elevational view of the apparatus of FIG. 1;
FIG. 3 is a graph relating the finger position to time, i.e., product count; and
FIGS. 4 and 5 are graphs relating finger assembly velocity to product count .